Data used in the following analysis were extracted from the database of the Hospital In-Patient Enquiry (HIPE) scheme maintained by the Economic and Social Research Institute.1  HIPE is a computer-based health information system designed to collect medical and administrative data regarding discharges and deaths from acute hospitals.2 Each HIPE discharge record represents one episode of care; each discharge of a patient, whether from the same or a different hospital, or with the same or a different diagnosis, gives rise to a separate HIPE record. The records therefore facilitate analyses of hospital activity rather than of the incidence of disease. HIPE does not record information on cases that attend accident and emergency units but are not admitted as inpatients. 

Number of deaths from overdose

The total number of overdose cases for the period 1996 to 2004 inclusive was 46,539.  Eighty of these cases died and have been excluded from this analysis. 

 Age group

Cases aged between 15 and 65 years inclusive are included in this analysis.  Figure 1 shows that the 20–24-year age group is at highest risk, with the incidence of overdose decreasing with age.  It is important to note the significant number of cases in the 15–19-year age group. 

Figure 1   Incidence of overdose by age group, 1996 to 2004

Area of residence

From 1999 to 2001 a steady increase in overdose cases was recorded among persons resident outside Dublin.  In 2002 there was a slight decrease among this population, followed by an increase in 2003 and then a significant decrease (18%) in 2004. Reported overdose cases among persons resident in Dublin decreased steadily between 2000 and 2004. 

Figure 2   Area of residence of overdose cases, 1996 to 2004

Most common drug category by type of overdose

Attempted suicide accounted from the majority (81%) of overdose cases reported through HIPE for the years 1996 to 2004 inclusive. Of these cases, 42% related to the use of a tranquillizer or other psychotropic-type drug and 39% related to intentional overdose with analgesics.  According to the 2005 annual report of the National Registry of Deliberate Self Harm Annual, 41% of all drug overdoses involved a minor tranquilliser, 32% involved paracetamol and 23% involved anti-depressants.2 

 Figure 3   Most common drug category, by type of overdose, 1996 to 2004

Gender

There were more overdose cases among females than among males.  A significant decrease in reported incidence of overdose among females (17%) and among males (15%) is evident between 2003 and 2004. 

Figure 4   Incidence of overdose by gender, 1996 to 2004

Opiates

Opiate-type drugs were involved in fewer less than 1% of cases reported for each year between 1996 and 2004.  Since 2002, the trend in accidental poisoning by opiates other than heroin has stabilised.  The number of cases of accidental poisoning by heroin decreased by 58% in the same period, from 19 in 2002 to 8 in 2004. 

Figure 5   Incidence of overdose involving opiate-type drugs, 1996 to 2004

Thirteen per cent more males than females overdosed using opiate-type drugs during the period 1996 to 2004.  A significant number (16%) of those who overdosed using opiate-type drugs were in the 15–19-year-old group; however, the majority (27%) were in the 20–24-year-old group, and the incidence decreased in successive age groups between 25 and 54 years.  Thirty-eight per cent of overdose cases involving an opiate-type drug occurred in the Dublin region. 

1. I would like to thank the ESRI for providing the data for the analysis included in this article.

2. The coding scheme used to code diagnoses for the years presented in this analysis was the International Classification of Diseases, 9th Revision, Clinical Modification, known as ICD-9-CM. Further information and reports on HIPE can be found on the Economic and Social Research Institute website at www.esri.ie

3. National Registry of Deliberate Self Harm Ireland (2005) Annual report 2005. Cork: National Suicide Research Foundation.